<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div>
    <span>1</span>
    <span>2</span>
    <span>3</span>
    <span>4</span>
    <span>5</span>
    <span>6</span>
</div>
</body>
<style>

    div{
        display: flex;
        width: 600px;
        height: 400px;
        background-color: rgba(112, 220, 203, 0.4);
        flex-direction: column;
        justify-content: center;
        /*我们需要一个侧轴居中*/
        align-items: center;
        /*align-items: flex-start;*/
        /*拉伸，但是子盒子不要给高度*/
        /*align-items: stretch;*/
    }
    div span{
        width: 150px;
        height: 100px;
        background-color: #eea068;
        margin: 10px;
    }
</style>
</html>